Method of treating mineral coal distillation benzol



Patented June 8, 1954 METHOD OF TREATING MINERAL COAL DISTILLATION 'BENZOL Joseph Carabasse, NOQllX-IQSrMiIIBS, Marcel Delassus, Mazingarbe, and Andre Mennessier, Bethune, France, assignors to Etablissement Public: Houilleres du Bassin du Nord et du Pas-de-Calais, Doua stitution of France i, France, an endowed in- No Drawing. Application May 1'7, 1949,

Serial No. 93,852

Claims priority, application France May 22, 1948 Our invention is concerned with a method of industrially treating benzol such as it can be separated from mineral coal distillation gases or tars. One is aware that crude benzol, e. g. such as it is removed from coke oven gases or obtained by driving off the lower-boiling fractions from coal tar, consists primarily of a mixture of arcmatic hydrocarbons such as benzene, toluene, the three xylenes, cthylbenzene and the many higher homologues of the same, amongst which cumene, pseudocumene, mesitylene, durene, and so on. It also contains many impurities, amongst which such non-saturated hydrocarbons as styrolene and indene, substances that contain oxygen (e. g. coumarone) or sulphur (e. g. mercaptans, thiophene or methylthiophene) and many more undesirable substances which are present in much smaller amounts.

Generally, the procedure which will lead to the best appreciation of the aforementioned raw material consists in producing:

1. High-purity benzene and toluene;

2. A fraction that boils Within a range of 4 or 5' degrees centigrade and that contains the three xylenes together with ethylbenzene, all of which vboil at quite close temperatures;

3. One or several fractions that consist of mix- 7 tures of the numerous aforementioned higher homologues, which fractions are generally referred to as solvent naphtha (12021-0 0;)

Now, in. order to confer a high commercial value upon these benzol constituents, it is necessary to strip the same carefully from the aforementioned impurities, notably from unsaturated hydrocarbons'that will progressively and spontaneously form colored gums'as well as from organic sulphur compounds which, even-where they are present as traces in thesaid products, will'm'ake the latter unsuitable for certain chemi cal processes.

The refining method as practiced inbenzoltreating plants consists instirring crude =benzol or rough benzol cuts once or-several-times-with as much concentrated sulphuric acid as is necessary to completely polymerize the unsaturated rage olumns whe eb pur p oducts 3 .2 Claims. (Cl. 202-57) well as commercial fractions satisfying the requirements of any given specification are obtained. As the residue of the distillation process there are finally obtained products which were resinified bythe action of thesulphuric acid and which constitute a more or less viscous black mass of little commercial value.

Such a procedure suffers from several serious inconveniences:

1. Some of the impurities that must be removed, e. g. thiophene, are attacked but slowly by highly concentrated sulphuric acid. Onthe other hand, also some aromatic hydrocarbons, above all amongst the higher-boiling highermolecular homologues, will react with sulphuric acid in the concentration and temperature conditions that are necessary tocompletely destroy the said thiophen'e. The consequence is that in the course of the refining step an appreciable percentage of valuable aromatic hydrocarbons are lost in the form of sulphonic acids.

2. Some of the unsaturated hydrocarbons, e. g. styrolene and homologues thereof, will condense in thepresence of sulphuric acid with such aromatic hydrocarbons as xylenes to 'homologues of the -l,l-.diphenylethane according to the equation:

The said homologues are oily and boil at temperatures higher than 300* C; They will ac- 3. The considerable temperature rise that at- 7 tends the action of the sulphuric acid upon the crude benzol enhances undesired sulphqnation reactions and increasesthelosses,

4. Spch polymerizable substances as indene and coumarone are converted into a black and viscous oil of but little value. "I fhe applicants have now found that these'inconveniences can beavoided by subjecting crude ybenzol, prior to any chemical treatment, toa

very strict fractionation leading to cuts having distillation characteristics corresponding to t ose required in pur p ecincts and t n jecting each particular fraction to a chemical treatment suited to its character.

1 o e o the main advant es o rn w meth is that it leads to higher yields .of very pure aromat c hy rocarb ns hile. the efin n i n as a Whole requires mu h less time Fractionation Fractionation A further important advantage is that by starting from one or several suitable fractions it becomes possible to obtain hard high-melting pale resins of high commercial value.

Various ways of carrying our method into effect will now be described in the following examples, it being understood that our invention is not limited merely to the treatment of benzol as referred to; nor is it to the use of the particular apparatus and reagents mentioned therein.

Example 1.-Crude benzol from coke oven gas was subjected to fractioning in continuous operation under atmospheric pressure or in a multistage column. The following cuts were obtained:

(a) Heads boiling within the 20-80 C. range (b) Crude benzene boiling within a 0.6 C. range Crude toluene boiling within a 0.95 C. range The residue thereafter was distilled under a vacuum in discontinuous operation and yielded a fourth fraction composed of crude xylenes and higher homologues thereof which distil between about 137 and 200 C.

A final residue remained in a small amount in the boiler which was due to the presence in the some of the heat.

Thereafter each fraction was subjected to the following treatments:

(0.) H eacls.This usually unimportant fraction may either be treated in order separately to obtain carbon disulphide, cyclopentadiene, a lowboiling gasoline and a resin, or else be converted into engine fuel.

(b) Crude benzene.This fraction was stirred for 15 minutes-with 2.5% by volume of 99.5%

sulphuric acid. After settling and removal of the acid sludge it was subjected once more to a similar treatment, then washed with water, neutralized with soda lye and finally redistilled without rectification. In this manner a very pure marketable benzol is obtained which complies with the most severe requirements:

(A. F. N.

O. R. method, B 6-11 standard) 96% on 0.3 C. range Specific weight 15/15 0.8840 Solidification point 5.4" C. 'Sulphonic acid index (M 0 Isalitine test for thiophene nil.

(0) Crude toZuene.This fraction was stirred for 15 minutes with 2% by volume of 96% acid. After settling and removal of the acid sludge it was washed with water, then with soda lye and finally redistilled without rectification. A very pure toluene was obtained the characteristics of which were as follows:

(A. F. N.

'O. R. method) 96% on 0.6 C. range Sulphuric acid index (1/1)- 0.1 Isalitine test for thicphene homologues Traces (d) 137-200 C. fraction-The said fraction, which contains most of the instable' constituents originally present in the benzol (e. g.

styrolene, indene, coumarone) may be treated in the known commercial manner with a view to convert the latter into marketable resins. This fraction may also be treated by any other method capable of simultaneously polymerizing the resinifiable constituents present therein.

Where the method just referred to is used the resin obtained consists of styrolene-indenecoumarone copolymers. Its properties, which confer a high commercial value upon it, are as follows:

Softening point (Kramer 8: Sarnows method) -120 C. Colour as a film water-white Colour as a thick layer pale yellow Molecular weight (Staudingers method) 300 to 3500 In the example just described the overall yield of benzene-l-toluene-i-xylenes+solvent naphtha is by about 5% higher than that which can be obtained by the former method. Moreover, about 2% of a pale and hard resin of high commercial value. The commercially worthless distillation residue is decreased by about 3% and the overall losses by about 2%.

Example 2.A method of very high interest is as follows: The crude benzol is subjetced to a pro-fractionation leading to:

(a) Heads boiling between 20 and 80 C. (1)) Crude benzene boiling within a 0.6 C. range (-0) Crude toluene boiling within a 0.9 C. range (d) Crude xylenes boiling between 137 and 144 C. boiling between 144 and about 200 C.

Thereafter fractions ((1), (b) and (c) are treated as set forth in Example 1. From the crude xylenes fraction most of the styrolene is removed by azeotropic distillation, and the residue is treated as set forth in said example, either alone or together with fraction (e).

Our invention is not limited to the treatment of coal distillation benzol such as it is obtained in coke ovens and coke gas plants. It is also applicable to gasolines such as are gathered in coal carbonization plants. Usually, the said gasolines which are more complex in their structure than benzols will not be treated for the obtainment of pure hydrocarbons. They will rather be reserved for the production of engine fuels. In the performance of the method to the said gasolines the number of fractions to separate depends on the number and character of the main constituents of the particular gasoline treated; the distillation ranges of said fractions willdepend on the character of the impurities to be removed; the procedure adopted for refining the fractions will be as follows: 7

(a) Fractions boiling up to C.The amount of acid and the concentration will be reduced to the minimum consistent with the required properties of the marketable products to be obtained. H

(b) Fractions boiling beyond 130 C.--There is a decided advantage in subjecting them to the copolymerization process as mentioned under Example 1. C

What we claim as our invention and desire to secure by Letters Patent is: V,

1. In a method of separating the pure hydrocarbon components from the crude'benzol frac- (e) Higher-molecular homologues I tion removed from the coking of coal by the fractionation of the crude benzol into a head fraction, a benzene fraction, a toluene fraction, and a residue containing xylenes, higher homologues of xylene and polymerizable styrolene, indene, coumarone components, followed by concentrated sulfuric acid treatment and redistillation to obtain the purified distillable components from the starting crude benzol, that improvement comprising distilling the crude benzol to obtain a head fraction distilling at a temperature up to 80 C., distilling a benzene fraction within about 0.6 0. range of the boiling point of benzene, distilling a toluene fraction within about a 095 C. range of the boiling point of toluene, subjecting each of the fractions to treatment with a small amount of concentrated sulfuric acid, removing the sulfuric acid from the fractions treated, and redistilling the acid-free fractions to obtain an improvement in the purity and yield of the benzene and toluene and in the quality of the styrene, indene, coumarone components in the distillation remainder.

2. A process as in claim 1 wherein the benzene traction boiling within a maximum temperature range of about 0.6 C. is treated with about 2 by volume of 99.5% sulfuric acid and the toluene fraction boiling within a maximum temperature range of about 0.95" C. is treated with about 2% by volume of about 96% sulfuric acid.

References Citedjin the file of this patent UNITED STATES PATENTS OTHER REFERENCES Chemistry of Coal Utilization, vol. II, pages 1198, 1199.

Foster, pages 130-132. 011 and Gas Journal, April 13, 1944. 

1. IN A METHOD OF SEPARATING THE PURE, HYDROCARBON COMPONENTS FROM THE CRUDE BENZOL FRACTION REMOVED FROM THE COKING OF COAL BY THE FRACTIONATION OF THE CRUDE BENZOL INTO A HEAD FRACTION, A BENZENE FRACTION, A TOULENE FRACTION, AND A RESIDUE CONTAINING XYLENES, HIGHER HOMOLOGUES OF XYLENE AND POLYMERIZABLE STYROLENE, INDENE, COUMARONE COMPONENTS, FOLLOWED BY CONCENTRATED SULFURIC ACID TREATMENT AND REDISTILLATION TO OBTAIN THE PURIFIED DISTILLABLE COMPONENTS FROM THE STARTING CRUDE BENZOL, THAT IMPROVEMENT COMPRISING DISTILLING THE CRUDE BENZOL TO OBTAIN A HEAD FRACTION DISTILLING AT A TEMPERATURE UP TO 80* C., DISTILLING A BENZENE FRACTION WITHIN ABOUT 0.6* C. RANGE OF THE BOILING POINT OF BENZENE, DISTILLING A TOULENE FRACTION WITHIN ABOUT A 0.95* C. RANGE OF THE BOILING POINT OF TOULENE, SUBJECTING EACH OF THE FRACTIONS TO TREATMENT WITH A SMALL AMOUNT OF CONCENTRATED SULFURIC ACID, REMOVING THE SULFURIC ACID FROM THE FRACTIONS TREATED, AND REDISTILLING THE ACID-FREE FRACTIONS TO OBTAIN AN IMPROVEMENT IN THE PURITY AND YIELD OF THE BENZENE AND TOLUENE AND IN THE QUALITY OF THE STYRENE, INDENE, COUMARONE COMPONENTS IN THE DISTILLATION REMAINDER. 